96 research outputs found
Schottky barrier heights at polar metal/semiconductor interfaces
Using a first-principle pseudopotential approach, we have investigated the
Schottky barrier heights of abrupt Al/Ge, Al/GaAs, Al/AlAs, and Al/ZnSe (100)
junctions, and their dependence on the semiconductor chemical composition and
surface termination. A model based on linear-response theory is developed,
which provides a simple, yet accurate description of the barrier-height
variations with the chemical composition of the semiconductor. The larger
barrier values found for the anion- than for the cation-terminated surfaces are
explained in terms of the screened charge of the polar semiconductor surface
and its image charge at the metal surface. Atomic scale computations show how
the classical image charge concept, valid for charges placed at large distances
from the metal, extends to distances shorter than the decay length of the
metal-induced-gap states.Comment: REVTeX 4, 11 pages, 6 EPS figure
Review: Nutritional ecology of heavy metals
The aim of this review is to focus the attention on the nutrition ecology of the heavy metals and on the major criticisms related to the heavy metals content in animal feeds, manure, soil and animal-origin products. Heavy metals are metallic elements that have a high density that have progressively accumulated in the food chain with negative effects for human health. Some metals are essential (Fe, I, Co, Zn, Cu, Mn, Mo, Se) to maintain various physiological functions and are usually added as nutritional additives in animal feed. Other metals (As, Cd, F, Pb, Hg) have no established biological functions and are considered as contaminants/undesirable substances. The European Union adopted several measures in order to control their presence in the environment, as a result of human activities such as: farming, industry or food processing and storage contamination. The control of the animal input could be an effective strategy to reduce human health risks related to the consumption of animal-origin products and the environmental pollution by manure. Different management of raw materials and feed, animal species as well as different legal limits can influence the spread of heavy metals. To set up effective strategies against heavy metals the complex interrelationships in rural processes, the widely variability of farming practices, the soil and climatic conditions must be considered. Innovative and sustainable approaches have discussed for the heavy metal nutrition ecology to control the environmental pollution from livestock-related activities
Milk yield and composition of late lactating dairy cows fed supplemental zinc (zinc soaps) and receiving bST
Plasma levels of somatotropin, somatostatin and metabolites in dairy cows fed a protected fat enriched diet
Ruolo degli oligoelementi nella risposta immunitaria della bovina da latte in transizione
- …